scholarly journals The cap size and shape of Arabidopsis thaliana primary roots impact the root responses to an increase in medium strength

2018 ◽  
Author(s):  
J. Roué ◽  
H. Chauvet ◽  
N. Brunel-Michac ◽  
F. Bizet ◽  
B. Moulia ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Primary Root ◽  
Root Cap ◽  
Size And Shape ◽  
Primary Roots ◽  
Medium Strength ◽  
Cell Layers ◽  
Root Responses ◽  
Mutant Lines

AbstractDuring root progression in soil, root cap cells are the first to encounter obstacles. The root cap is known to sense environmental cues, making it a relevant candidate for a mechanosensing site. An original two-layer medium was developed in order to study root responses to growth medium strength and the importance of the root cap in the establishment of these responses. Root growth and trajectory of primary roots of Arabidopsis thaliana seedlings were investigated using in vivo image analysis. After contact with the harder layer, the root either penetrated it or underwent rapid curvature, enabling reorientation of the root primary growth. The role of the root cap in tip reorientation was investigated by analyzing the responses of Arabidopsis mutant roots with altered caps. The primary root of fez-2 mutant lines, which has fewer root cap cell layers than wild-type roots, showed impaired penetration ability. Conversely, smb-3 roots of mutant lines, which display a higher number of root cap cells, showed enhanced penetration abilities. This work highlights that alterations in root cap shape and size affect the root responses to medium strength.HighlightThe analysis of the growth and orientation of Arabidopsis thaliana mutant roots affected in root cap size and shape showed that properly formed root cap is required to trigger the root responses to medium strength.AbbreviationsCOLcolumella;LRCLateral Root Cap;SISharpness Index;SMBSOMBRERO.

scholarly journals Root cap size and shape influence responses to the physical strength of the growth medium in Arabidopsis thaliana primary roots

2019 ◽  
Author(s):  
J Roué ◽  
H Chauvet ◽  
N Brunel-Michac ◽  
F Bizet ◽  
B Moulia ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Growth Medium ◽  
Root Cap ◽  
Arabidopsis Mutants ◽  
Physical Strength ◽  
Size And Shape ◽  
Primary Roots ◽  
Root Responses ◽  
Shape Influence

Analysis of the growth and orientation of roots of Arabidopsis mutants with differing root cap sizes and shapes indicates that the form of the cap affects root responses to variations in the strength of the growth medium.

Graviresponsiveness and cap dimensions of primary and secondary roots of Ricinus communis (Euphorbiaceae)

1984 ◽  
Vol 62 (8) ◽  
pp. 1767-1769 ◽  
Author(s):  
Randy Moore ◽  
John Pasieniuk
Keyword(s):  
Castor Bean ◽  
Ricinus Communis ◽  
Primary Root ◽  
Root Cap ◽  
Primary Roots ◽  
Secondary Roots

After branching from the primary root, secondary roots of castor bean (Ricinus communis) grow laterally for 15–20 mm, after which they bend downward (i.e., become positively gravitropic). During the first 10 mm of growth, the lengths of caps of secondary roots increase from 120 ± 26 to 220 ± 28 μm. Although this increase is statistically significant (P < 0.1%), the resulting secondary roots are only minimally graviresponsive. A subsequent doubling of the lengths and widths of the root caps (i.e., to 420 ± 34 and 450 ± 41 μm, respectively) is positively correlated with the onset of gravicurvature. The graviresponsiveness and dimensions of caps of positively gravitropic secondary roots are not significantly different from those of positively gravitropic primary roots. These results indicate that (i) a statistically significant increase in the length and length:width ratio of a root cap does not necessarily result in the root becoming positively gravitropic, (ii) there may be a minimum cap length and (or) width necessary for graviresponsiveness, and (iii) the degree of graviresponsiveness exhibited by a particular root may be related to the size of its root cap.

scholarly journals A Method Enabling Comprehensive Isolation of Arabidopsis Mutants Exhibiting Unusual Root Mechanical Behavior

2021 ◽  
Vol 12 ◽  
Author(s):  
Hiroshi Tojo ◽  
Aki Nakamura ◽  
Ali Ferjani ◽  
Yusuke Kazama ◽  
Tomoko Abe ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Mechanical Behavior ◽  
Molecular Mechanisms ◽  
Primary Root ◽  
Land Plants ◽  
Root Penetration ◽  
Wild Type ◽  
Arabidopsis Mutants ◽  
Primary Roots ◽  
Similar Phenotype

Root penetration into soils is fundamental for land plants to support their own aboveground parts and forage water and nutrients. To elucidate the molecular mechanisms underlying root mechanical penetration, mutants defective in this behavior need to be comprehensively isolated; however, established methods are currently scarce. We herein report a method to screen for these mutants ofArabidopsis thalianaand present their phenotypes. We isolated five mutants using this method, tentatively namedcreep1tocreep5, the primary roots of which crept over the surface of horizontal hard medium that hampered penetration by the primary root of the wild type, thereby forcing it to spring up on the surface and die. By examining root skewing, which is induced by a touch stimulation that is generated as the primary roots grow along a vertical impenetrable surface, the fivecreepmutants were subdivided into three groups, namely mutants with the primary root skewing leftward, those skewing rightward, and that growing dispersedly. While the majority of wild type primary roots skewed slightly leftward, nearly half of the primary roots ofcreep1andcreep5skewed rightward as viewed from above. The primary roots ofcreep4displayed scattered growth, while those ofcreep2andcreep3showed a similar phenotype to the wild type primary roots. These results demonstrate the potential of the method developed herein to isolate various mutants that will be useful for investigating root mechanical behavior regulation not only in Arabidopsis, but also in major crops with economical value.

Chemotaxis of zoospores of Phytophthora megasperma to primary roots of alfalfa seedlings

1978 ◽  
Vol 56 (7) ◽  
pp. 795-800 ◽  
Author(s):  
C. C. Chi ◽  
F. E. Sabo
Keyword(s):  
Trifolium Pratense ◽  
Primary Root ◽  
Root Hairs ◽  
Red Clover ◽  
Root Surface ◽  
Root Cap ◽  
Root Tips ◽  
Phytophthora Megasperma ◽  
Root Area ◽  
Primary Roots

Chemotaxis of the zoospores of Phytophthora megasperma was studied on freshly excised primary root tips of 2-day-old seedlings of nine alfalfa (Medicago sativa L.) cultivars and four other legume species. The highly susceptible cultivars Saranac, Algonquin, and Vernal attracted masses of zoospores within minutes after being placed into fresh zoospore suspensions. The moderately susceptible cultivars Iroquois, Angus, and Thor displayed less severe en masse zoospore accumulation. Resistant cultivars Apollo, Agate, and to a lesser degree WL-318 exhibited minor chemotaxis.Zoospores were strongly attracted to the region of elongation, immediately above the root cap area. Relatively few zoospores, if any, were attracted to the root cap and older regions of the roots. Zoospores were not attracted to root hairs. Within 0.5-1 h, zoospores attracted to the roots began to encyst and germinate. Germ tubes always originated from the side of cysts closest to the root surface, and all showed unidirectional growth towards the root.Very weak or no chemotactic responses of zoospores to nonhost legume plants of white sweet clover (Melilotus alba Desr.), red clover (Trifolium pratense L.), bird's-foot trefoil (Lotus corniculatus L.), and soybean (Glycine max (L.) Merr. cv. Vansoy) were observed. Roots of susceptible alfalfa seedlings pretreated in boiling water did not attract zoospores.Injured, susceptible alfalfa roots displayed a strong preferential attraction around a wounded root area. Varying zoospore densities occurred at different distances from the wound. Wounded, resistant alfalfa roots showed slightly more zoospore accumulation than the uninjured resistant roots.The magnitude of chemotaxis and response time appear to be related to the susceptibility or resistance of the young, primary roots of alfalfa seedlings.

scholarly journals Tornado1 and tornado2 are required for the specification of radial and circumferential pattern in the Arabidopsis root

Development ◽  
2000 ◽  
Vol 127 (15) ◽  
pp. 3385-3394
Author(s):  
G. Cnops ◽  
X. Wang ◽  
P. Linstead ◽  
M. Van Montagu ◽  
M. Van Lijsebettens ◽  
...  
Keyword(s):  
Root Hair ◽  
Lateral Root ◽  
Cell Function ◽  
Primary Root ◽  
Root Cap ◽  
Radial Pattern ◽  
Root Hair Cell ◽  
Cell Layers ◽  
Default State ◽  
Hair Cell Differentiation

The cell layers of the Arabidopsis primary root are arranged in a simple radial pattern. The outermost layer is the lateral root cap and lies outside the epidermis that surrounds the ground tissue. The files of epidermal and lateral root cap cells converge on a ring of initials (lateral root cap/epidermis initial) from which the epidermal and lateral root cap tissues of the seedling are derived, once root growth is initiated after germination. Each initial gives rise to a clone of epidermal cells and a clone of lateral root cap cells. These initial divisions in the epidermal/lateral root cap initial are defective in tornado1 (trn1) and trn2 plants indicating a requirement for TRN1 and TRN2 for initial cell function. Furthermore, lateral root cap cells develop in the epidermal position in trn1 and trn2 roots indicating that TRN1 and TRN2 are required for the maintenance of the radial pattern of cell specification in the root. The death of these ectopic lateral root cap cells in the elongation zone (where lateral root cap cells normally die) results in the development of gaps in the epidermis. These observations indicate that TRN1 and TRN2 are required to maintain the distinction between the lateral root cap and epidermis and suggest that lateral root cap fate is the default state. It also suggests that TRN1 and TRN2 repress lateral root cap fate in cells in the epidermal location. Furthermore, the position-dependent pattern of root hair and non-root hair cell differentiation in the epidermis is defective in trn1 and trn2 mutants. Together these results indicate that TRN1 and TRN2 are required for the maintenance of both the radial pattern of tissue differentiation in the root and for the subsequent circumferential pattern within the epidermis.

scholarly journals Two Expansin Genes, AtEXPA4 and AtEXPB5, Are Redundantly Required for Pollen Tube Growth and AtEXPA4 Is Involved in Primary Root Elongation in Arabidopsis thaliana

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 249
Author(s):  
Weimiao Liu ◽  
Liai Xu ◽  
Hui Lin ◽  
Jiashu Cao
Keyword(s):  
Arabidopsis Thaliana ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Cell Walls ◽  
Root Elongation ◽  
Expression Patterns ◽  
Primary Root ◽  
Pollen Grains ◽  
Tube Growth ◽  
Cell Wall Binding

The growth of plant cells is inseparable from relaxation and expansion of cell walls. Expansins are a class of cell wall binding proteins, which play important roles in the relaxation of cell walls. Although there are many members in expansin gene family, the functions of most expansin genes in plant growth and development are still poorly understood. In this study, the functions of two expansin genes, AtEXPA4 and AtEXPB5 were characterized in Arabidopsis thaliana. AtEXPA4 and AtEXPB5 displayed consistent expression patterns in mature pollen grains and pollen tubes, but AtEXPA4 also showed a high expression level in primary roots. Two single mutants, atexpa4 and atexpb5, showed normal reproductive development, whereas atexpa4atexpb5 double mutant was defective in pollen tube growth. Moreover, AtEXPA4 overexpression enhanced primary root elongation, on the contrary, knocking out AtEXPA4 made the growth of primary root slower. Our results indicated that AtEXPA4 and AtEXPB5 were redundantly involved in pollen tube growth and AtEXPA4 was required for primary root elongation.

scholarly journals Seed Gamma Irradiation of Arabidopsis thaliana ABA-Mutant Lines Alters Germination and Does Not Inhibit the Photosynthetic Efficiency of Juvenile Plants

Dose-Response ◽  
2020 ◽  
Vol 18 (4) ◽  
pp. 155932582097924
Author(s):  
Darya Babina ◽  
Marina Podobed ◽  
Ekaterina Bondarenko ◽  
Elizaveta Kazakova ◽  
Sofia Bitarishvili ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Growth Response ◽  
Dose Range ◽  
Fine Tuning ◽  
Plant Tolerance ◽  
Inhibitory Effects ◽  
Γ Irradiation ◽  
Photosynthetic Responses ◽  
Mutant Lines

Plant growth response to γ-irradiation includes stimulating or inhibitory effects depending on plant species, dose applied, stage of ontogeny and other factors. Previous studies showed that responses to irradiation could depend on ABA accumulation and signaling. To elucidate the role of ABA in growth and photosynthetic responses to irradiation, lines Col-8, abi3-8 and aba3 -1 of Arabidopsis thaliana were used. Seeds were γ-irradiated using 60Co in the dose range 50-150 Gy. It was revealed that the dose of 150 Gy affected germination parameters of aba3 -1 and Col-8 lines, while abi3-8 line was the most resistant to the studied doses and even showed faster germination at early hours after γ-irradiation at 50 Gy. These results suggest that susceptibility to ABA is probably more important for growth response to γ-irradiation than ABA synthesis. The photosynthetic functioning of 16-day-old plants mainly was not disturbed by γ-irradiation of seeds, and no indication of photosystem II photoinhibition was noticed, revealing the robustness of the photosynthetic system of A. thaliana. Glutathione peroxidase activity and ABA concentrations in plant tissues were not affected in the studied dose range. These results contribute to the understanding of germination and photosynthesis fine-tuning and of mechanisms of plant tolerance to ionizing radiation.

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